During a time such as COVID-19, it is important to keep ourselves in our healthiest state. With more recoveries occurring each day, potential treatments including the use of zinc have arisen. I was intrigued to know more about zinc and its benefits for the immune system as I had never really heard of zinc’s applications. As more is discovered regarding zinc and its benefits for COVID-19, it is important to understand its known effects.
What is zinc?
Zinc is an essential nutrient required by the body to stay healthy. Essential nutrients are nutrients that cannot be produced or stored by the body. Thus, one must obtain zinc through their diets or necessary supplements. Zinc can be found in cells throughout the body and aids the immune system in fighting off bacteria and viruses. Additionally, zinc is needed to create proteins, heal wounds, and maintain proper smell and taste. Zinc is especially important during pregnancy, infancy, and childhood to help the body develop and grow. Furthermore, zinc is required for the catalytic activity of approximately 100 enzymes and plays a role in immune function. A daily intake of zinc is required to maintain a healthy state as the body lacks a zinc storage system.
Zinc-Deficiency Discovery in Humans
The essentiality of zinc for plants and animals has been known for decades; however, the essentiality for zinc in humans was not recognized until 40 years ago in the Middle East. In 1869, the essentiality for zinc for growth was observed in Aspergillus niger, a species known as “black mold.” Next, in 1933, the essentiality for zinc was discovered in rats. By 1960, the essentiality for zinc in animals was reported, but it was considered dubious that a zinc deficiency would have a clinical impact on humans. In 1961, however, a zinc-deficiency was discovered in an Iranian male and is now known to be an important issue of malnutrition. The 21-year old Iranian male farmer presented with anemia, hypogonadism, and dwarfism. Hypogonadism is a condition in which the body does not produce enough testosterone which is necessary for male growth and development. The farmer’s diet consisted of milk, unrefined flat bread, and milk. Soon afterwards, a similar syndrome was reported in Egyptian adolescents. After administration of zinc diets and supplements, improved growth and corrected hypogonadism were reported. The anemia was responded to by oral iron supplements.
Groups at High Risk for Zinc Deficiency
Adolescents: There is a great requirement for zinc during adolescence as this is the time of puberty. In girls, this pubertal growth spurt occurs between ages 10 and 15. The growth spurt occurs between ages 12 and 15 in boys. Even after puberty and growth spurt has stopped, zinc is needed to replenish depleted zinc tissue pools.
Infants and children: Infants and children are more susceptible to zinc deficiencies because there is an increased zinc requirement during growth. Breast-fed infants receive sufficient zinc for the first 5 to 6 months. However, after this, foods containing absorbable zinc must be consumed.
Pregnant women: Pregnant women are predisposed to zinc deficiency due to increased nutritional demands during this time. These demands are increased during lactation, thus an increased intake of zinc is required. For pregnant women, dosages as low as 60 mg/day, were insufficient in meeting necessary zinc needs.
Elderly: Zinc intakes in the elderly are often inadequate. This can be attributed to poor zinc nutrition in their diets. For instance, reduced consumption of zinc-rich foods such as red meat result in reduced zinc. Studies have also suggested the efficiency of zinc absorption may decrease as one gets older.
Clinical Manifestations of Zinc Deficiency
Zinc deficiencies correlate to several clinical conditions and manifestations. The multitude of biochemical functions zinc is involved in the cells, allows for a broad range of physiological conditions to arise as a result of zinc deficiencies. The epidermal, gastrointestinal, central nervous, immune, skeletal, and reproductive organ system are known to be affected by zinc deficiencies. One of the most reported clinical features of zinc deficiencies were the impairment of physical growth and development. The most significant effects of these impairments occurred during pregnancy, infancy, and adolescence which is when the body’s demands for zinc are the highest. Infections such as diarrhea, pneumonia, and malaria have also been reported. Degenerative changes associated with the elderly may also partly be due to zinc deficiencies. These include delayed wound healing, neurological and physiological changes, as well as a reduction in immunocompetence. Rough skin, poor appetite, mental lethargy, and cell-mediated immune dysfunctions have been clinically reported as well.
Zinc and Immunity
Zinc plays a large role in the immune system. Zinc is extremely important for the normal development and function of cells facilitating innate immunity, neutrophils, and NK cells. Neutrophils are a type of white blood cell that aid in healing damaged tissue and fighting against infections. NK cells, or natural killer cells, are a type of lymphocyte/white blood cell. Natural killers cells control several types of tumors and microbial infections by limiting their spread and tissue damage caused by these invasions. Macrophages (type of white blood cell), phagocytosis (cell ingestion of bacteria) , intracellular killing (performed through phagocytosis), and cytokine (regulators of immunity) production also rely on zinc and are affected by zinc deficiencies. Zinc also functions as an anti-oxidant and stabilizes the cell membrane. This suggests zinc plays a role in preventing free-radical induced injury during the inflammatory process.
Recommended Intakes of Zinc
The recommended intake of zinc differs with age, gender, and interactions with medication. The table below shows the tolerable upper intake levels for zinc.
Interactions with medication
- Antibiotics: Quinolone and tetracycline antibiotics interact with zinc in the gastric tract. These antibiotics inhibit zinc absorption. Thus, the medication should be taken at least 2 hours before or 4-6 hours after ingesting zinc to minimize any interactions
- Penicillamine: Zinc can reduce and the absorption of penicillamine. Penicillamine is a drug used to cure rheumatoid arthritis. Zinc supplements should be taken 2 hours before or after taking penicillamine.
Sources of Zinc
There are many sources of zinc that can be easily incorporated into one’s diet. In general, meat, poultry, and seafood are rich in zinc. Plant foods such as legumes and whole grains are also good sources of zinc.
- Shellfish
- Oysters
- Crab
- Lobster
- Beef
- Poultry
- Pork
- Legumes
- Nuts
- Seeds
- Whole grains
- Fortified breakfast cereals
Zinc supplements such as pills and lozenges can be taken, but they should not be substituted for foods rich in the nutrient. High doses can also result in vomiting and nausea.
References
“Office of Dietary Supplements – Zinc.” NIH Office of Dietary Supplements, U.S. Department of Health and Human Services, ods.od.nih.gov/factsheets/Zinc-Consumer/.
Prasad, Ananda S. “Discovery of human zinc deficiency: its impact on human health and disease.” Advances in nutrition (Bethesda, Md.) vol. 4,2 176-90. 1 Mar. 2013, doi:10.3945/an.112.003210
Prasad, Ananda S. “Zinc in human health: effect of zinc on immune cells.” Molecular medicine (Cambridge, Mass.) vol. 14,5-6 (2008): 353-7. doi:10.2119/2008-00033.Prasad
Roohani, Nazanin et al. “Zinc and its importance for human health: An integrative review.” Journal of research in medical sciences : the official journal of Isfahan University of Medical Sciences vol. 18,2 (2013): 144-57.
“Zinc.” The Nutrition Source, 1 Nov. 2019, http://www.hsph.harvard.edu/nutritionsource/zinc/.
Journey To Cure 